1. Field of the Invention
This invention concerns tubes used in heat exchangers which are finned in order to increase their heat exchanging properties as well as a method and apparatus for rolling finned tubes and subsequently working the fins to obtain a Y or T shape.
2. Description of the Prior Art
Finned tubes are known generally in the art. For example, German Offenlegungschrift No. 1501656 shows a finned tube in which the fins have indentations provided in the fins at their outer circumference. Such tubes are beset with difficulties in storage and transport as well as in installation of the tube into tube plates and into support washers which are used in mounting the tubes in heat exchangers. Furthermore, the use of such tubes in tube bundle evaporators can be troublesome since the crevices between adjoining fins of the tubes which are located in relatively high positions of the evaporators tend to collect bubbles rising from below. These bubbles lodge in these crevices and prevent an optimum heat exchanging operation. The rising bubbles are able to enter into the relatively wide openings in the crevices between adjoining indentations and thereby prevent the evaporation surfaces from making optimum contact with the liquid.
U.S. Pat. No. 3,299,949 shows a power vacuum tube having longitudinal T-formed fins used for cooling. These tubes must, however, be arranged in a perpendicular fashion in order to utilize the so-called "thermo syphon effect." A utilization of this principal in regard to evaporators consisting of bundles of tubes is not possible since in regard to these evaporators the tubes must be arranged horizontally.